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1500 questions
38
votes
11 answers
Examples of number theory showing up in physics
Are there any interesting examples of number theory showing up unexpectedly in physics?
This probably sounds like rather strange question, or rather like one of the trivial to ask but often unhelpful questions like "give some examples of topic A…
Joe Fitzsimons
- 8,475
38
votes
3 answers
Deriving the Lagrangian for a free particle
I'm a newbie in physics. Sorry, if the following questions are dumb. I began reading "Mechanics" by Landau and Lifshitz recently and hit a few roadblocks right away.
Proving that a free particle moves with a constant velocity in an inertial frame…
Someone
- 483
38
votes
2 answers
Should a superconductor act as a perfect mirror?
I have been told that metals are good reflectors because they are good conductors. Since an electric field in conductors cause the electrons to move until they cancel out the field, there really can't be electric fields in a conductor.
Since light…
user42012
- 932
38
votes
3 answers
What happens when anti-matter falls into a black hole?
Let's say a black hole of mass $M$ and a very compact lump of anti-matter (not a singularity) also of mass $M$ are traveling toward each other. What does an outside observer see when they meet?
Will they blow themselves apart in a …
Schwern
- 4,534
38
votes
2 answers
How does one correctly interpret the behavior of the heat capacity of a charged black hole?
Note: Although I have a provided an "answer" to the question, I did not resolve all the questions in this post satisfactorily. I invite anyone willing and able to provide a better answer, which I would be glad to accept instead.
Consider the…
Danu
- 16,576
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38
votes
2 answers
Kubo Formula for Quantum Hall Effect
I'm trying to understand the Kubo Formula for the electrical conductivity in the context of the Quantum Hall Effect.
My problem is that several papers, for instance the famous TKNN (1982) paper, or an elaboration by Kohmoto (1984), write the…
Greg Graviton
- 5,397
38
votes
9 answers
Why singularity in a black hole, and not just "very dense"?
Why does there have to be a singularity in a black hole, and not just a very dense lump of matter of finite size? If there's any such thing as granularity of space, couldn't the "singularity" be just the smallest possible size?
Per
- 530
38
votes
5 answers
What is the physical meaning of the affine parameter for null geodesic?
For time-like geodesic, the affine parameter is the proper time $\tau$ or its linear transform, and the geodesic equation is
$$\frac{\mathrm d^{2}x^{\mu}}{\mathrm d\tau^{2}}+\Gamma_{\rho\sigma}^{\mu}\frac{\mathrm dx^{\rho}}{\mathrm…
Siyuan Ren
- 5,132
38
votes
5 answers
Shine a beam of light horizontally, drop a stone from same height - would both hit the ground at the same time?
If a beam of light was shone horizontally, and simultaneously a stone was dropped from the same height, would they both hit the ground a the same time?
Of course on Earth they would not, but let's imagine a land mass large enough for the light not…
user59315
38
votes
7 answers
Conservation of energy and Doppler effect?
From what I understand, the frequency of light coming from a source moving towards an observer increases. From $ E=h\nu $ , this implies an increase in the energy of each photon.
What really is confusing, is where does that extra energy come from?…
S L
- 1,591
38
votes
8 answers
Gibbs free energy intuition
What is Gibbs free energy? As my book explains:
Gibbs energy is the energy of a system available for work.
So, what does it want to tell? Why is it free? Energy means ability to do work. What is so special about this energy? Can anyone simply…
user36790
38
votes
16 answers
"Reality" of length contraction in SR
I was in argument with someone who claims that length contraction is not "real" but only "apparent", that the measurement of a solid rod in its rest reference frame is the "real length" of the rod and all other measurements are somehow just…
Zeus
- 3,543
38
votes
3 answers
Can all fundamental forces be fictitious forces?
After reading many questions, like
this and this, I wonder:
Is it possible to consider the other fundamental forces too, the electroweak interaction and the strong interaction or ultimately the unification of these, to be fictitious forces like…
Costantino
- 995
38
votes
5 answers
What is the most efficient information storage?
What is the most efficient way to store data that is currently hypothesized? Is it theoretically possible to store more than one bit per atom?
Until Floris' comment, I hadn't considered that efficiency is dependent on what you're trying to optimize.…
Tyler
- 499
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38
votes
1 answer
What is the theoretical lower mass limit for a gravitationally stable neutron star?
I ask here intentionally not for the size of the smallest possible observed size of neutron stars, which corresponds approximately to the well-known Chandrasekhar-limit for the upper limit of the white dwarfs. This is defined by the minimal size of…
peterh
- 8,872